Recently, metal-supported cells have been developed actively (for example, see Patent Literature 1). The metal-supported cells exhibit excellent properties such as higher mechanical strength, more rapidly starting up, and higher resistance to re-dox characteristics than conventional electrolyte-supported cells or electrode-supported cells. Stabilized zirconia by the addition of rare earth atoms or the like have been used as solid electrolytes contained in the metal-supported cells. Conventionally, the solid electrolytes of the stabilized zirconia by the addition of rare earth atoms or the like needed to be sintered at a high temperature. Therefore, in production of the metal-supported cells, when the solid electrolyte layers and the metal supports are sintered together at the high temperature, it's sometimes bound to cause problems of metal support deterioration and peeling between the solid electrolyte layers and the metal supports.
Bi2O3 has been known as a sintering agent in forming of the solid electrolytes containing the stabilized zirconia by the addition of rare earth atoms or the like. Patent Literature 2 describes solid-state zirconia materials containing Sc2O3, Bi2O3 and CeO2 as solutes, and the content of Bi2O3 and CeO2 being 0.5-5 mol % in total. Further, Patent Literature 3 describes solid electrolyte materials having the composition formula of x mol % Sc2O3−y mol % Bi2O3−(100−x−y) mol % ZrO2 (5≤x≤15, 0.5≤y≤3, x+y≥8). The solid electrolyte materials are used as a raw powder of raw materials for solid electrolytes. In the raw powder, Bi2O3 dissolves in ZrO2, and 5-15 mol % of Sc2O3 also dissolves in ZrO2 to form a solid solution. The materials are prepared by the coprecipitation process, and sintered at 970-1500° C. to form the solid electrolyte.
In metal-supported cells preparation, it has been required that the metal-supported cells can be well sintered at lower temperature such as 1200° C. or less in condition of layered on metal supports, and that the sintered metal-supported cells have a high ion-conductivity, a high adhesion between the metal supports and solid electrolyte layers to suppress an interfacial peeling between them, and stable cell characteristics.